The invention relates to a mechanism for driving a transporting device comprising a frame by human force and/or with a mechanical driving source, whereby a part to be rotated by human force is coupled, by resiliently deformable member, to a driven part, which is to be rotated so as to drive the transporting device, whilst monitoring member are provided for determining the angular displacement between the two parts, with a view to influencing the mechanical driving source through control member.
Such a mechanism is described in U.S. Pat. No. 5,024,286, more in particular used in a bicycle equipped with an auxiliary motor. Although the present application also describes an embodiment wherein the mechanism is used in a motor-assisted bicycle, it will be apparent that the mechanism according to the invention can also be used in other vehicles and/or craft, for example in a motor-assisted pedal boat.
The bicycle known from U.S. Pat. No. 5,024,286 has two discs extending parallel to each other and being provided with openings at their circumference, the discs being used for determining the angle of displacement between the part rotated by human force and the part being driven. In the unloaded position of the parts the openings in the one discs are covered by parts of the other disc. During operation the discs will generally rotate more or less with respect to each other, as a result of which the aperture parts of the discs will overlap each other to a larger or smaller extent. An optical sensor is used for detecting the extent to which the aperture parts of the discs overlap as well as the passage of the overlapping openings, in order to generate signals for influencing the control member of the mechanical driving source, all this as explained in the above-mentioned U.S. Pat. No. 5,024,286, the contents of which are incorporated herein by reference.
Although the device may be satisfactory per se, the fact that the use of an optical sensor requires power constitutes a drawback, whilst such a mechanism is furthermore highly sensitive to fouling of the optical sensor.